1. Field of the Invention
The present invention relates to a method for producing a negative charging toner.
2. Description of the Related Art
In an electrophotographic or an electrostatic recording image forming apparatus, an image can be formed on a piece of paper by supplying a toner that is charged with a predetermined polarity and to a predetermined amount of charge, to an image forming section thereby distributing the toner over the paper so as to form the image, through the effect of an electric field, and then fixing the toner thus distributed over the paper.
The toner may be a magnetic two-component toner, in which the toner is charged through frictional charging by a magnetic carrier, or a non-magnetic mono-component toner, which is charged by friction with a contact section of the image forming apparatus, without using any magnetic carrier. Non-magnetic mono-component toners are advantageous for reducing the size of the image forming apparatus.
Generally known such non-magnetic mono-component toners include toners having a main component of polyester resin, which is a binder resin. When using such toners as the negative charging toners, it is necessary to employ a negatively chargeable charge control agent (CCA) or charge control resin (CCR).
Known conventional wet process methods for producing such toners include, for instance, suspension polymerization methods, ester extension methods, solution suspension methods, emulsification aggregation methods and the like. In the production of a negative charging toner using the polyester resin as the binder resin, the polyester resin is negatively chargeable. Hence, after the production of the base particles, it is not possible to fix the negatively charged charge control resin microparticles or the like to the surfaces of the base particles made of polyester resin within a liquid. For this reason, the toner base particles are produced by mixing beforehand the binder resin with the charge control agent or the like (Japanese Patent Application Laid-open No. 2005-62818).